What are the best practices for battery longevity?

All devices that use Lithium Ion batteries suffer the same pitfalls. A chemical reaction takes place which stores and releases the energy.

A good model is a simple rubber band! You stretch it to store kinetic energy and then when you release it the stored energy is released (think rubber band plane you played with when you where a kid) letting the plane fly off. Of course you want it to fly longer so you wind up the band even tighter pushing it more and more. At some point the band snaps!

Now lets look at this same rubber band but this time we let it sit in a drawer for a few months you wind it up but instead of storing the normal amount of windings it snaps sooner! What happened! The rubber broke down (ozone in the air) rotted it.

So what we have here is two failure possibilities over winding and age of the rubber band.

Thats the same problem we face with Lithium Ion batteries! So they can fail from over use as well as age. Then the trick is to reduce the extreme deep charge cycles as that causes more of a thermal load within the chemical reaction of conversion. Likewise, excessive load converting the chemical energy back to electrical energy will do the same. Simply put its like driving a car! Drive at 55 MPH Vs racing at 90 or sudden stopping.

As an example I have a 2012 MacBook Pro which I mostly use plugged in note the age and cycles here:

So my usage has biased AC vs Battery power, letting me extend its life. While that works for a laptop sitting on a desk mostly, it doesn’t work for a cellphone as an example my iPhone 6:

Here you can see I’ve run up the cycle count past 250! But you’ll note the design capacity is not too bad as I try hard not to let the phone to run below 1/3 of charge which has given me 5 great years of use and likely at least 4~5 more!

Even still replacing your phones battery OnePlus 7 Pro 拆解 (similar to your OnePlus 7) is a cakewalk! Vs what I face! So don’t worry, if you are a bit rougher than I am with my phone use.